In 2001 the US EPA lowered the maximum contaminant level for arsenic in drinking water from 50 ppb to 10 ppb, based on studies indicating the lower limit would prevent a significant number of cancer deaths and other illnesses. The EPA estimates that there are approximately 2,294 community and over 1,000 non-community (factories, hospitals, military bases, etc.) water systems serving 10,000 people or less that will have to install some form of arsenic treatment system. New approaches, particularly simple adsorption-based technologies, are needed to provide cost effective treatment options for these small water suppliers. In Phase I, ADA showed that its Amended Silicate(tm) arsenic sorbent, distinguished by the formation of nanoscale akaganeite crystallites on an inert silicate substrate, had 1.5 to 4 times greater capacity for arsenic versus commercial media in arsenic-contaminated drinking water. In addition, the material captures As(III) and As(V), and is insensitive to pH over the normal range of drinking water. Cost estimates indicate the new sorbent is less expensive than existing commercial products. In Phase II, the team will analyze the fundamental chemistry of the iron-based Amended Silicate(tm) material and demonstrate a complete arsenic removal system based on the use of the sorbent. The system design will utilize the unique physical properties of the Amended Silicate(tm) in a fluidized sorbent contactor. Fluidized contactors provide some key process advantages for dealing with fouling species such as silica, and allow for continuous removal, regeneration, and make up of the sorbent. Pilot-scale fluidized sorbent units will be fabricated and tested in laboratory and field settings. These prototypes will be small capacity to simplify testing requirements, but will be fully automated and will incorporate all components of a full-scale design. Data from the Phase II demonstration will be used by ADA and its commercialization partner to design cost-effective treatment systems for community water suppliers. ADA has teamed with Kinetico Inc., a leading supplier of water treatment systems, to bring this technology to market for the impending 2006 compliance deadline.